Abstract Factory in PHP

<?php

/*

 *  Abstract Factory classes

 */

 

interface iFactory {

    public function createInstance();

}

 

abstract class DB_Abstraction_Factory {

    protected $settings = array();

    protected function __construct() {

        $this->settings = Settings::getInstance();

    }

 

    abstract public function createInstance();

}

 

class DB_Abstraction_Factory_ADODB extends DB_Abstraction_Factory implements iFactory {

    public function __construct() {

        parent::__construct();

    }

    public function createInstance() {

        require_once('/path/to/adodb_lite/adodb.inc.php');

        $dsn = $this->settings['db.dsn'];

        $db = ADONewConnection($dsn);

        return $db;

    }

}

 

class DB_Abstraction_Factory_MDB2 extends DB_Abstraction_Factory implements iFactory {

    public function __construct() {

        parent::__construct();

    }

    public function createInstance() {

        require_once 'MDB2.php';

        $dsn = $this->settings['db.dsn'];

        $db = MDB2::factory($dsn);

        return $db;

    }

}

 

interface iAbstractFactory {

    public static function getFactory();

}

 

class DB_Abstraction_AbstractFactory implements iAbstractFactory {

    private function __construct() 	

    }

    public static function getFactory() {

        $settings = Settings::getInstance();

        require_once('iFactory.php');

        require_once('DB_Abstraction_Factory.php');

        switch($settings['db.library'])

        {

            case 'adodblite':

                require_once('DB_Abstraction_Factory_ADODBLITE.php');

                $factory = new DB_Abstraction_Factory_ADODBLITE();

            break;

            case 'mdb2';

                require_once('DB_Abstraction_Factory_MDB2.php');

                $factory = new DB_Abstraction_Factory_MDB2();

            break;

        }

        return $factory;

    }

 }

 

/*

 *  Client's code

 */

 

// instantiate Abstract Factory

$abstractfactory = new DB_Abstraction_AbstractFactory();

 

// fetch a concrete Factory (decision handled in Abstract Factory static method)

$factory = $abstractfactory::getFactory();

 

// use concrete Factory to create a database connection object from

// the selected database abstraction library

$db = $factory->createInstance();

?>